This invention relates to the manufacture of cathode ray tubes for television receivers. The invention is embodied in an apparatus for testing the hermetic qualities of the seal between the front panel and funnel of the cathode ray tube, commonly termed the "frit" seal.
Prior art methods of testing the hermetic qualities of the seal utilize a standard fixture designed for an individual sized cathode ray tube. One limitation with the standard fixture is that only one size tube may be tested in each particular fixture, requiring multiple fixtures to accommodate the variety of tube sizes contemporaneously manufactured in the manufacturing process. An operator physically sets each tube to be tested face down upon the standard fixture and releases linkage allowing a spring-like device to close in around the frit seal and substantially contact the frit for the duration of the test. Prior art methods utilize a flat spring or a wire gauze "Brillo pad"-type structure in the fixture.
The test voltage is applied to the anode of the cathode ray tube. The spring or gauze serves as the ground completing the test circuit. Any defect or break in the seal will cause a breakdown through the seal to transfer current to the grounded wire gauze or flat spring surrounding the seal. The flat spring or wire gauze apparatus is limited in that the contact established with the seal around the entire periphery of the cathode ray tube is interrupted due to the qualities of the spring or gauze-type structure. Neither are sufficiently flexible to contact the frit seal at all points around the tube. At any point around the tube whre the frit seal does not contact the spring or gauze structure, the seal is not being tested and the possibility of a defective seal being passed by the test method is enhanced.